The present invention is related to an electrical assembly and device. In particular, the present invention relates to an electrical assembly and device comprising an element exhibiting positive temperature coefficient behavior.
Since the electrical assembly or device of the present invention comprises a positive temperature coefficient element, it can be used in applications where conventional electrical assemblies or devices comprising a positive temperature coefficient element are used, for example, as a circuit protection device which is assembled in an electric circuit and breaks the circuit if an abnormal current passes through the circuit. Alternatively, the electrical assembly or device of the present invention can be assembled in a circuit to open a relay switch which is assembled in the circuit in series with a load, when a resistance increases.
Elements exhibiting positive temperature coefficient behavior (hereinafter called xe2x80x9cpositive temperature coefficient elementxe2x80x9d or xe2x80x9cPTC elementxe2x80x9d) generally have a characteristic that the resistivity increases in response to a temperature increase in a comparatively narrow temperature range, and can be used as, for example, a circuit-protection element.
Devices comprising PTC elements have no mechanical components, and when abnormal current passes through the circuit, the resistance increases to shut off the circuit. Thus, such devices are used as circuit protection devices.
In the case of circuit protection devices, it is desirable to make the resistance of the device as small as possible in order to increase the holding characteristic (the minimum current at which the device actuates). In order to decrease the resistance, it may be contemplated to decrease the thickness of the PTC element, or to increase the area of the PTC element.
There is a limit to decreasing the thickness of the PTC element, and devices currently used to protect circuits such as integrated circuits comprise PTC elements having a thickness close to the limit. If the area of the PTC element is increased, on the other hand, the area of the device is also inevitably increased. As integrated circuits become more highly integrated, the size of each element is required to be minimized and the area of the device cannot be increased beyond a certain level.
One object of the present invention is to provide an electrical assembly and device comprising a PTC element, where the area of the PTC element is increased without increasing the projected area as a whole.
Another object of the present invention is to provide a simple and economical method for producing such an electrical assembly and device.
The present invention provides the following electrical assembly, the electrical device and the method for producing the same:
[I] An electrical assembly comprising
(1) a body member which
(a) is composed of an electrically insulating material, and
(b) includes at least two cavities;
(2) spaced-apart electrically conductive contact members, there being at least two contact members within each cavity;
(3) a plurality of electrical devices, each device being positioned in one of the cavities and each cavity having at least one device positioned therein; each device comprising spaced-apart electrically conductive terminals in physical and electrical contact with the contact members within the cavity in which the device is positioned; and at least one of the devices being a PTC device (including a bimetallic switch);
(4) a plurality of electrically conductive connection members which are secured to the body member, each contact member being in physical and electrical contact with at least one connection member; and
(5) electrically conductive terminals through which the assembly can be electrically connected into a circuit, each terminal being
(a) secured to the body member, and
(b) in physical and electrical contact with at least one connection member;
the connection member being electrically connected to each other so that, when the terminals are connected into a circuit, at least two of the devices are connected in parallel.
[II] An electrical device comprising a pair of electrodes (terminal members), at least three substrates (constituting a body), and PTC elements inserted between the substrates (corresponding to the cavities of the body), each PTC element having metal layers (terminals) on both surfaces,
wherein each of the two outermost substrates has a metal layer (conductive contact member) on the inner surface, the two metal layers (conductive contact members) being in electrical contact with the respective metal layers (terminals) of the PTC elements facing said metal layers of the outermost substrates,
the other substrates have metal layers (conductive contact members) on both surfaces, such metal layers (conductive contact members) being in electrical contact with the respective metal layers (terminals) of the PTC elements facing said metal layers (conductive contact members)of the substrates, and
all the PTC elements are connected in parallel with the electrodes (terminal members).
[III] An electrical device as described in [II], wherein the number of substrates is three,
each of the outer substrates has a metal layer (conductive contact member) on the inner surface, the two metal layers (conductive contact members) being electrically connected to one of a pair of electrodes (terminal members) and in electrical contact with the respective metal layers (terminals) of the PTC elements facing said metal layers (conductive contact members) of the outer substrates, and
the center substrate has a metal layer (conductive contact member) on both surfaces, such metal layers (conductive contact members) being electrically connected to the other electrode (terminal member) and in electrical contact with the respective metal layers (terminals) of the PTC elements facing said metal layers (conductive contact members) of the center substrate.
[IV] An electrical device as described in [III], wherein the three substrates are integrally bonded to one surface of a back plate,
the metal layers (conductive contact members) on the inner surfaces of the two outer substrates are electrically connected by an electrode (conductive connection member) formed on the outer surfaces of said outer substrates and the outer surface of the back plate, and
the metal layers (conductive contact members) formed on both surfaces of the center substrate are electrically connected by an electrode (conductive connection member) formed at least in a through-hole provided on the back plate and on the outer surface of the back plate.
[V] An electrical device as described in [III], wherein the three substrates are integrally connected to one surface of the back plate,
the metal layer on the inner surface of one of the outer substrates is connected to an electrode formed on the outer surface of said substrate and the outer surface of the back plate,
the metal layers on the inner surfaces of both end substrates are electrically connected to each other by a metal band formed on the inner surface of the back plate, and
the metal layers formed on both surfaces of the center substrate are electrically connected by an electrode formed at least in a through-hole provided on the back plate and on the outer surface of the back plate.
[VI] A method for producing an electrical device as described in [IV], comprising the steps of:
integrally forming the back plate and the three substrates from a resin,
forming metal layers on the inner surfaces of the outer substrates and on both surfaces of the center substrate,
forming a first electrode, which is connected to the two metal layers on the inner surfaces of the outer substrates, on the outer surfaces of the outer substrates and the outer surface of the back plate, and forming a second electrode, which is connected to the metal layers on both surfaces of the center substrate, at least in the through-hole provided on the back plate and on the outer surface of the back-plate, and
inserting positive temperature coefficient elements having metal layers on both surfaces between the substrates.
[VII] A method for producing simultaneously two switches as described in [V], comprising the steps of:
integrally forming the back plate and five substrates,
forming metal layers on the inner surfaces of the outermost substrates and the both surfaces of other three substrates,
forming a first electrode, which is connected to each of the metal layers on the inner surfaces of the outermost substrates, on the outer surfaces of the outermost substrates and the outer surface of the back plate, and forming a second electrode, which is connected to the metal layers on both surfaces of each of the intermediate substrates sandwiched between the outermost substrates and the center substrate, at least in the through-hole provided on the back plate and on the outer surface of the back plate,
forming a metal band, which electrically connects each of the metal layers on the inner surfaces of the outermost substrates to a metal layer on either surface of the center substrate, on the inner surface of the back plate,
inserting PTC elements having metal layers on both surfaces between the substrates, and
cutting the center substrate in a direction perpendicular to the direction of the thickness.